Method of producting clay bodies and apparatus used



Nov.- 10,1925. 1,561,002

G. w. LAPP V 7 METHOD OF PR ODUCING CLAY BODIES AND APPARATUS USED Original Filed 27, 1919 2 sauu-shm 1 Y'IVITNEISASES v I v I v Alia? w l atented Now 1 0, 1925. v A I UNITED-STATES PATENT OFFICE.

GRbVER w. LAPP, or LE BOY, NEW YORK, assmuoa no my msuuuron couramr, 1110., A courom'rron or mew YORK.

mn'rnon or rnonucme ona'z norms in arraiwrususnn.

' Original application filed August 27, 1919, SeriaLNo. 820,163. Divided and this application filed June :1, I 1922. Serial No. 567,027. I

To allwhom z't may concern: I. 7 complete vitrification or a loss of strength 65 Be it known that I, GROVERW. LAPP, a in the finished ware will be the consequence. "citizen of the United States, and a resident I believe that the source of this air or vof Le Boy, in the county of .Genesee and the gas has not been fully appreciated, nor 6 State of New York, have made a new and has direct removal thereof under the presuseful Invention in Methods of Producing ent methods been accomplished. When it is ClayBodies and Apparatus Used, of which known that the total air or other gas in the the following is a specification. claymay be over twenty-five per cent of the This invention relates to ceramics and volume of the clay body the possible injury- 1 more particularly to the treatment of clay to the bodg on. this account can be readily or clay bodies for use in producingv ceramic ap reciate i I wares and apparatus used therefor. art of the air contained in the clay slip "This application is a division of applicaas well as in the pugged cla is in the tion Serial No. 320,163 filed by me on August form of bubbles minutely subdlvided dur- 1 27,1919. ing the mixingoperations and retained in In the preparation of clay bodies for use the. body mixture. Another part'o'f the air 70 in the production of ceramic wares it is now present is in actual solutionin the water of customary to mix the ingredients with water the mixture. The water generally used for to form a slip, then to sift the slip mixing is cold and under a pressure above through a screen into an agitator storage atmospheric pressure so that it readily recistern from which the slip is pumped into tains in solution a considerable percentage 75 a filter press where excess water is removed 'of its own volume'of dissolved air or gas. in order to obtain a cake of clay of the When reduced to atmospheric pressure and average moisture desired. In order to make raised in temperature'in the mixing tub or this cake-material more uniform in moisture 'blung'er the Water actually becomes satucontent, it is then 'pugged through a mill rated with dissolved air and gas. My ex- 80 fitted with'knife blade propellers arran ed periments have led me tobelieve that the in a screw progression or else it is knea ed clay as now worked is fairly oozing with between a table and rollers. In both of these air. I '30 working processes some of the trapped air WVhen the clay is pugged .or kneaded the is eliminated and some of it digested by mechanical wor expended thereon further 5 and incorporated in the clay. increases its temperature and causes it to These work'ng processes up to a certain discharge more of the dissolved air or gas point soften the clay and refine the grain which together with air from trapped air thereof, but after such point the clay bebubbles trails in the wake of the cutting 1 comes stifier and of more open grain and at knives of the pug mill and causes thelami- 90' they same time noticeably warmer. The nated structure referred to. Even when dis- [cause of this deterioration is due to air tinct laminations are not formed the intiin the clay. a innate incorporation of'air with the clay The presence of air or other gases in the causes the grain of over-worked clay to i 1 plastic clay often causes it'to issue from the be opened and the body to become short 96 'ug miles a laminated body or' structure or mealy instead of smooth'and having the and even when laminations are not formed buttery feel of good-working plastic clay.

the pugging or kneading as now carried on Such clay often becomes so stiif that it rep cannot be carried farenou h to develop fuses to flow freel through the die of the full in the body the'smoot ness of grain, pug mill nozzle an when over worked be- 100 uni orm density, maximum homogegleity, tween the rollers and table it also becomes and bond' strength des red- Lack of unistiff and inferior.

, formity causes serious shrinkage and crack- "It has been customary in order to improve 0 ing in-drying 'and the presence of variable clay bodies to age the material after it is v I pore. spaced causes variable shrinkage and removed from the filter press. In this aginaccurate sizing of the product. The highing process the clay is batted together in or the porosity of tlfe unburned body the a amp cellar whereit is left for a period higher will be the burning shrinkage and less of time and in this way the gas and air pore space is apparently very slowly dissolved,

. cay.

dilfused and liberated at the surface of the clay; at the same time the particles appear to settle together more compactly.

In the manufacture of certain chemical porcelains it has been found that six months aging is not suflicient to produce results but that when eight or ten months are allowed the poi-celains can be successfully made. This process of agin has been ascribed to a little understood tlieory of bacterial action but my experiments lead me to believe that the improvement in the clay bodies obtaiiiedby aging is largely due to the reduction of the air content to a point which still leaves much to be desired it the clay is to withstand further intensive mechanical treatment.

Under the prevailing practices the plastic clay body is fed through a pug mill eniploying for finishing a single spiral pushing member or twin worms with axes arranged longitudinally of the stream flow. The pug mill employing a single spiral pusher leaves a weak center to the clay and in the mill using two worms the worms do not intermesh beyond their axes of rotation and two weak centers are therefore produced. \11 objectionable feature in pugged clay 18. its laminated structure in the shape of spiral layers which are advanced or pushed ahead at the center of the pug and retarded at the outside on account of friction on the walls of the pug nozzle or die. The cleavage spaces between laminations represent the wake of the pugging members and these s aces are filled with the air present in the These laininations are usually worse at the center because, after they are formed by the spiral out, the pressure is less at the center and the air therefore flows in that direction. At the same time the clay at the sides is subjected to both pressure and 1011- shearing motion which tend to heal gitudinal the clay and scatter the air layer.

Believing that the prevailing practices in the clay industries are the fertile causes of much obscure trouble, an object of this inventionis to provide a process whereby the air or gas content of the clay bodies may be more thoroughly removed than has hith'erto been possible.

A further object is to provide a process whereby the clay bodies can be safely worked to higher temperatures than heretofore.

A still further object is'to provide a process whereby the air or gas also the moisture content of clay bodies may be evenly distributed throughout the body.

A still further object is to provide a method for improving the quality of slip for use in the process of casting clay bodies.

A still further object is to provide a process whereby the aging of clay bodies may be dispensed with.

in chamber 15.

In carrying out my process the gas or air may be removed from the mix by subjectmg the water with which the ingredients are to be mixed or the slip after the water is added or the plastic clay to a vacuum. The preferred method is to suck the slip from the agitator storage system through a closed chamber to which an air extracting pump or other device is connected so that as the slip flows through the vacuum chamber the dissolved and free air and gas which it contains will be removed or extracted. The slip tree from gas and air, is then forced directly into the filter press and, after the clay has been filter-pressed, the leaves may be fed to a much higher temperature than is nowpossible.

Instead, however, of using a pug mill or a kneading machine I prefer to place the press cakes in a closed cylinder connected up to an air extracting pump and then to force the press cakes into a solid air free mass. I then force the compacted mass in the form of a stream through a mixing device provided with moving members which cut across the clay stream past its center of flow. A screen of suitable mesh is placed between said cylinder and the mixing device in order to remove therefrom any shreds, lint or other foreign matter which it may contain.

For the purposes of this application I have shown apparatus by means of which my process may be carried out and in the drawings, Figure l is a diagrammatic illustration of a portion of such apparatus, Fig. 2 is a more or less diagrammatic illustration in longitudinal sectionof a portion of the apparatus and Figs. 3, 4 and 5 are detail views of portions of the same.

In carrying out my process the clay materials, consisting of any desired mix, are fed from a hopper 6 to a ball mill or blunger 7, into which water is'also fed through a controlled pipe 8. The mixed slip material from the blunger is conducted by means of a pipe 9 onto an agitated screen or lawn 10 as is now common. The screened slip passes by means of a hopper 11 and pipe 12 into an agitator storage cistern 13 provided withthe customary power driven agitator- 14. From the bottom of the agitator cistern the slip is sucked up into the top of a closed chamber 15 by means of a sufficient vacuum Pump 16 withdraws the slip from the bottom of chamber 15 through pipe 17 and forces it into filter press 18 through pipe 19.

The blunger, the sdreen, the agitator cis-' tern and the filter vpress may be of ordinary construction operating in the usual manner.

' cally constant level of slip in chamber at her 15.

all times when there is sufficient-vacuumwhether pump 16 is forcing slip into the filter press or not. When the level of slip rises float 2-it rises and causes valve 23 toshut off or to reduce the lnflOWDf slips to cham- After the clay body has. been removed from the filter press, it is thoroughly mixed in order that the moisture content and any pore space stillremaining may be evenly distributed throughout the clay body. Clay press cakes formed by'this process are practically air free and they can be pugged. or kneaded to produce a better quality of body than can be made from cakes not formed from air free slip. However, when the leaves of clay are fed to the pug mill or rolling table, a large percentage of volume of air is trapped and is only partly elimi nated during theearly stages of working.

The remainder is occluded in the ,mass of and becomes subdivided into minute cla blebs. It is diflicult to prevent this air content from r ppearing in the wake o-f'the cutting me ers of the pug mill in the form of cleava es separating the clay into laminations.

From the foregoing considerationsit will be seen that the elimination of this air trapped during mechanical mixing is an important step in theproduction of an ideal air free body. 1

The device which I have chosen for carrying out this mixing step of my process con sists of two cylindrical chambers 25 and 26 connected by a, cylindrical passage, 27 .of reduced cross section. Chamber 25' is provided with a head 28, a piston 29 and'a hand operated screw 36 for forcing piston 29 toward passage 27 in order to compact the clay body and force it through said passage 2'7 e Chamber 25 is also preferably connected through a pipe 31 to a vacuum pump or other airremoving d,ev1ce.-

' The removal of air from the receptacle or chamber 25 is a preliminary step, the receptacle oeing exhausted as soon as the filterpress cakes are in lace therein. It is desirable to remove t e air so that the cakes will not trap air when they are compressed into acompact mass in the succeeding operation. For this reason the receptacle is so formed that it is not completely filled by means of a the shape of the filter-press cakes is-such as to provide ample-connected space between the cakes and also between the cakes and the walls of the receptacle to insure a complete evacuation of'the receptacle and a minimum trapping of air.

Chamber 26 is provided with a head 33 and a piston 34 to which a threaded rod 35 is. revolv'ably attached, a split nut 36 carried by head 33 is adapted to either engage threaded rod 35 or to be disengaged therefrom.

Passage 27 connecting chambers 25 and 26 is protected by a screen 25? and is provided ably consisting of two ring-like displacer members 40 and 41 mounted on trunnions WhlCh project through the passage walls.

with a mixing or kneading device prefer- The axes of these trunnions stand at right angles one to the other. The ring-like members through their trunnions are geared together by means of a gear train 42 whioh is driven by power. It will be noted that theseringdike members in rotating in'the clay stream (the stream moving from cylinder 25 to cylinder 26) traverse the stream past its center of flow so that the stream is cut across past its center whereby a thorough kneading or mixing takes place and this is accomplished without the formation of laminations. The mixed stream issuing from passage 27 emerges into chamber 26 gradually displacing or moving piston 34: away from passage 27. After chamber 26 truded through a die or nozzle, or if desired, the operation. may be reversed and the clay forced from the chamber 26 by means of screw 35 (after closing split nut 36 and after removing screen 25*) through passage 27 in the reverse direction into chamber 25 displacing piston 29 (split nut 30 having been released for that purpose). By carrying on this operation of Iorcing the clay body back and forth from one chamber to the other (which chambers with passage 27 form a closed system) the working and refinement of the clay body may be carried to any extent desired without the intrusion of air.

The type of transverse mixing mechanism shown in one form in Fig. 2 comprising the cylinder '27 and the moving displacer memis filled withthe thor- .oughly mixed and kneaded clay it is extoward the center. Other types of mixing devices have not this transverse intermixing power so that portions of material at the outside remain largely outside and the center of flow retains its center position. The result is that clay from one part of-the stream ture may be removed or extracted at any point in the process, but it is preferable to remove them just before the slip enters the filter press. If desired, vacuum chamber 15 may be formed in the nature of a jet condenser chamber so that'the slip entering the same will be broken up into spray thus facilitating the removal of the air or other gases by means of the vacuum pump.

In place of a vacuum pump it will be understood that an ejector type of pump, a \Vestinghouse-Leblanc pump, or any suit- I able device for creating and maintaining a relatively high vacuum may be used.

The same sort of a device may be used in connection with chamber 25 and when so used it will be; preferable to place a valve between the extracting device and chamber 25 in order to close off the passage to the extracting'device during the compression and compacting of the press cakes.

The importance of having plastic material free from gas is vital in the production of ceramic wares. The presence of gases in material for molded insulation, for rubber, for food products, for paints and a variety of plastic bodies represents an impurity in some cases or is a foreign element which weakens the structure of the material by prevention of proper bonding and by increasing the pore space.

The scope of this invention and its application should not be limited to plastic material for ceramic wares but should apply to the preparation of other plastic materials.

Having thusdescribed my invention, what I claim is:- e 1. That step in the art of preparing cla for use in producing ceramic ware, which consists in subjecting a moving mass of clay in plastic state to a mixing action in which portions of the mass are moved across the longitudinal axis thereof.

2. That step in the art of preparing plastic material for use in producing ceramic ware,

state to flow as in a stream and in mixing the material of the stream by means of displacer members which are caused to cross the stream past its center of flow.

tions of the mass are moved from one side thereof to the other and crosswise of its longitudinal axis. g

4. The method of preparing material for use in the production of ceramic ware, which consists in forcing plastic material from one container to another through a relatively constricted passage and during its travel through such passage in causing the material to move from one side of said passage to the other across the major axis thereof.

5. The method of preparing material for use in the production of ceramic ware, which consists in forcing plastic material from one container to another through a-relatively restricted passage, in screening such material prior to its. entrance to said passage and in causing the material traversing said passage to move about two axes located at approximately right angles one to the other.

6. The method which consists in compacting filterpress cakes of. material within a container maintained at sub-atmospheric pressure, in forcing said material from such container through a relatively restricted passage to an expansible container, in expanding said latter container as it fills with such material, and in kneading such material in its travels through'said passage;

7 The method of preparing plastic material for use in the production of ceramic ware, which consists in occasioning a flow of said material in a well defined stream and in subjecting the material of the moving stream to a mixing action by displacing portions thereof from one side to the other and across the axis of the stream.

8. The method of preparing plastic materialfor use, which consists in extruding a stream of material from an enclosing chamber and thereby occasioning a flow of the material through a confining passage and in subjecting the'extruded material moving through the passage to a mixing action 'by displacing portions'of the material from one side to the other and across the axis of the stream flowing through the passage.

9. A method of'preparing plastic material for use, which consistsin confining the material in a chamber, 'extrudingthe material through an orifice with which the chamber is provided by reducing the volumetric capacity of the chamber, and in subjecting the extruded material to a mixing action while moving in response to the extruding Jforce. which consists in causing material in plastic i 10. A method of preparing plastic material which consists in compacting the plastic material in a chamber from which gaseous fluids have been withdrawn, and extruding the material from the chamber while isolat- Lactose ing the extruded material from gaseous fluids.

11. A method of producing a gas-free plastic material which consists in compacting gas-free particles of plastic material in a chamber, from which the gaseous content has been substantially removed, extruding compacted material from the chamber, and subjecting the extruded material to a mixing action while excluding gaseous fluid.

- 12. 'I he method of producing substantially gas free plastic material which consists in compacting substantially gas-free particles of plastic material in a vacuum chamber, extruding the material from the chamber by reducing the volumetric capacity of the chamber, screening the material extruded and subjecting the screened material to a mixing'action, while isolating it from gaseous fluid such asair.

13. A method of preparing plastic material for use, which consists in extruding a stream of material, causing the extruded material to fill and flow through a confining passage, and in subjecting the material traversing the passage to a mixing action by causing portions thereof to move across the axis of the stream traversing the passage.

14. The method of preparing plastic material for use in the production of ceramic .ware, which consists in confining the material in a closed chamber and compacting the material within the chamber and extruding it therefrom by reducing the volume of the chamber and in subjecting the material extruded to a kneading action as it moves in response to the extruding force.

15. In combination in a plastic material mixing device, a compacting-chamber, having a delivery port formed therein, a passage vfor receiving material delivered through said port, and a kneading device lo cated in said passage.

16. In combination in a plastic material mixing device, a compacting chamber, having a delivery port formed therein, a passage for receiving material delivered through said port, and a kneading device located in said passage comprising means moving back and forth across said passage in the line of material flow therethrough.

17 A mixing device for plastic material comprising a passage, means for forcing material through the passage, and a kneading device in said passage comprising means movable approximately at right angles across and through the axis of said passage.

18. In combination in a plastic materlal mixing device, a chamber having an extrusion port formed therein, a passage communicating with said port, a kneadlng device located in said passage, and means for extruding material through said port and said passage.

19. In combination in a plastic material mixing device, a passage, a screen in said passage, a kneading device in said passage comprising means movable across the axis of said passage, and means for forcing material through said screen and said passage.

20. A compacting and extruding device for plastic material, comprising a chamber having a port for the delivery of material, means for removing gaseous fluid from said chamber, means for subjecting plastic material within said chamber to mechanical pressure and thereby extruding it through said port, a second chamber communicating with said port and receiving material therefrom and means for enlarging the capacity of said second chamber as it receives plastic-material.

21. In combination in an apparatus for treating plastic material, two chambers each adapted to receive plastic material, a restricted passage establishing communication between said chambers, means for forcing plastic material from one chamber to the other through said passage and means for kneading the material traversing said passage.

22. An apparatus for treating plastic material comprising two air excluding chambers, a restricted passage establishing communication between said chambers, means for withdrawing gaseous fluid from said chambers, and means for reducing the volumetric capacity of one chamber while increasing the volumetric capacity of the other and thereby extruding plastic material through said passage.

23. apparatus for treating plastic material, comprising two air excluding chambers, a restricted passage establishing communication between said chambers, means for reducing the internal volume of one chamher and increasing the internal volume of the other and for thereby forcing material through said passage, and a kneading device in said passage.

24. An apparatus for treating plastic material comprising two air excluding cylin ders, each provided with a port, a piston located in each cylinder, a passage connecting the ports, means for reciprocating said pistons to force material from one chamber to the other back and forth through said passage.

In testimony whereof, I have hereunto subscribed my name this 2nd day of June,

GBOVER W. LAPP. 

